Core drilling allows sampling of subterranean materials from various depths to be obtained for many purposes. For example, drilling a core sample and testing the retrieved core helps determine what materials are present or are likely to be present in a given formation. For instance, a retrieved core sample can indicate the presence of petroleum, precious metals, sand, and other desirable materials. Accordingly, core samples can be used to determine the desirability of further exploration and/or mining in a given area.
In sonic core drilling processes, variable frequency vibration is created by an oscillator. The vibration is then mechanically transferred to the drill string of the core barrel and/or casing. The vibration is transmitted in an axial direction down through the drill string to an open-faced drill bit. As a result, the drill string may be rotated and/or mechanically pushed as it is vibrated into the subsurface formation.
Often, sonic core drilling processes are used to retrieve a sample of material from a desired depth below the surface of the earth. Although there are several ways to collect core samples, core barrel systems are often used for core sample retrieval. Core barrel systems include an outer tube with a coring drill bit secured to one end. The opposite end of the outer tube is often attached to a drill string that extends vertically to a sonic drill head that is often located above the surface of the earth. The core barrel systems also may include an inner polycarbonate tube located within the outer core barrel. As the drill bit cuts formations in the earth, the inner tube can be filled with a core sample. Once a desired amount of a core sample has been cut, the inner tube, core barrel, and core sample can be brought up through the drill string and retrieved at the surface.
The sonic drill head may include high-speed, rotating counterbalances that produce resonant energy waves and a corresponding high-speed vibration to be transmitted through the drill string to the core barrel. As a result, the sonic drill head can vertically vibrate the core barrel. In addition, the drill head can rotate and/or push the core barrel into the subsurface formation to obtain a core sample. Once the core sample is obtained, the core barrel (containing the core sample) is retrieved by removing the entire drill string out of the borehole that has been drilled. Once retracted to the surface, the core sample may then be removed from the core barrel.
In a sonic wireline drilling process, the core barrel and the casing are advanced together into the formation. The casing again has an open-faced drill bit and is advanced into the formation. However, the core barrel (inner tube) does not contain a drill bit or connect to a drill string. Instead, the core barrel mechanically latches inside of and at the bottom of the casing and advances into the formation along with the casing. When the core sample is obtained, a drill operator can retrieve the core barrel using a wireline system. Thereafter, the drill operator can remove the core sample from the core barrel at the surface, and then drop the core barrel back into the casing using the wire line system. As a result, the wireline system eliminates the time needed to trip the drill rods and drill string in and out of a borehole for retrieval of the core sample.
Conventionally, upon detecting the presence of subterranean desirable materials, such as precious metals, sand and the like, an open pit mine is dug. In open pit mining, a large pit is dug and the overburden material positioned over the desirable materials is removed and hauled to a different location. However, forming an open pit mine is very time-consuming and expensive. Often an extensive dewatering system is required. There is also a large carbon footprint as millions of tons of overburden material removed from the open pit are trucked away. Further, there can be large capital costs in excavation equipment and infrastructure such as roads in order to form the open pit. Moreover, in some instances the open pit can be refilled, increasing cost as the removed overburden material is returned to the pit.
Thus, there is a need in the art for systems and methods for removing desirable subsurface materials without the need to dig an open pit mine to remove the overburden waste material. The present invention fulfills these needs and provides further related advantages as described herein
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.